Two well-known methods of drying granular material such as grain are the bin layer dryer method and the batch-in-bin type method. The former method utilizes a dryer with a fan and a heat unit which dries the granular material by forcing heated air through a perforated bottom floor of a bin and then upwardly through successive layers of the granular material added to the bin, thereby absorbing moisture and thus reducing the moisture content in the material. Since the heated air is forced into the bin from beneath the first layer, it is obvious that the lower levels in the bin are subjected to several repetitions of the flow of the drying air. Moreover, a bin layer dryer system requires a substantial amount of time to dry a full bin of granular material, and there is always the danger of overheating or overdrying the material in the lower layers.
The batch-in-bin dryer system is an improvement on the bin layer dryer method, and in this method, a single layer is dried on the perforated floor of the dryer bin, and then transferred to a storage bin. This overcomes the disadvantages of the bin layer dryer method in that each layer is subjected to drying only once. However, one of the disadvantages of this system is that an entire batch must be dried before any of it can be removed for replacement by a new batch.
More recently efforts have been made to provide continuous-flow dryers for granular material, one such apparatus being disclosed in U.S. Pat. No. 3,634,949 to Robert A. Louks. In this apparatus, a cylindrical housing is provided with a downwardly directed cone having a perforated wall portion at the lower part thereof, and a second smaller perforated cone is positioned within the first cone near the bottom thereof to define an annular conical space therebetween. Grain is fed into this space, and as it moves down the space to the bottom of the outer cone, warm air is forced across the annular conical space through the perforated wall portions to dry the grain moving along the cones.
While this apparatus is readily adaptable for drying such grains as feed corn, it does not permit the precise control required for the drying of seed grain, and particularly seed corn.
It has become increasingly recognized among those skilled in the art of handling seed grain that grain for use as seed must be handled much more carefully than grain which is to be used simply for feed or other food purposes. In particular, it has been found that the quality of the grain, particularly with respect to the percentage of the grain which germinates and the ability of the grain to withstand storage, depends to a large extent on the moisture content and the particular manner in which the seed has been dried.
This is particularly important for seed grain such as seed corn which must be removed from the ear, i.e. shelled, after it has been dried so as to be packaged for distribution for use as seed.
Applicant has found that in order to obtain seed corn with the best characteristics for germination and storage, and ear corn, i.e. the corn in the form of ears with the kernals still on the ears, should be dried to a moisture content of from about 12 to about 13% by weight. It has been found that when the ear corn has this moisture content, it is not only readily shelled, but the seed corn thus obtained has outstanding characteristics with respect to germination and ability to withstand storage.
It would be of great benefit to the art of handling seed grain, and particularly, seed corn, if an apparatus could be provided which would dry ear corn to a range of moisture content which would result in good properties of the seed corn shelled from the ear.